# Question: Data were collected during a step direction experiment in the biomechanics

Data were collected during a step-direction experiment in the biomechanics laboratory at Hope College. The goal of the study is to establish differences in stepping responses between healthy young and healthy older adults. In one part of the experiment, the subjects are told in what direction they should take a step. Then, when given a signal, the subject takes a step in that direction, and the time it takes for them to lift their foot to take the step is measured. The direction is repeated a few times throughout the testing, and for each subject, a mean of all the “liftoff” times in a certain direction is calculated.

The mean liftoff times (in thousandths of a second) for the anterior direction, ordered for your convenience, are as follows:

(a) Construct a back-to-back stem-and-leaf display. Use stems 3•, 4∗, . . . , 9∗.

(b) Use the Wilcoxon statistic to test the null hypothesis that the response times are equal against the alternative that the times for the young subjects are less than that for the older subjects.

(c) What outcome does a t test give?

The mean liftoff times (in thousandths of a second) for the anterior direction, ordered for your convenience, are as follows:

(a) Construct a back-to-back stem-and-leaf display. Use stems 3•, 4∗, . . . , 9∗.

(b) Use the Wilcoxon statistic to test the null hypothesis that the response times are equal against the alternative that the times for the young subjects are less than that for the older subjects.

(c) What outcome does a t test give?

**View Solution:**## Answer to relevant Questions

In Exercise 8.2-10, growth data are given for plants in normal air and for plants in CO2-enriched air. Those data are repeated here: In this exercise, we shall test the null hypothesis that the medians are equal, namely, H0: ...Let X1, X2, ... , X8 be a random sample of size n = 8 from a Poisson distribution with mean λ. Reject the simple null hypothesis H0: λ = 0.5, and accept H1: λ > 0.5, if the observed sum 8i=1 xi ≥ 8. (a) Compute the ...Let X1, X2, . . . , Xn be a random sample of Bernoulli trials b(1, p). (a) Show that a best critical region for testing H0: p = 0.9 against H1: p = 0.8 can be based on the statistic c) What is the approximate value of β = ...A biologist is studying the life cycle of the avian schistosome that causes swimmer’s itch. His study uses Menganser ducks for the adult parasites and aquatic snails as intermediate hosts for the larval stages. The life ...A random survey of 100 students asked each student to select the most preferred form of recreational activity from five choices. Following are the results of the survey: Test whether the choice is independent of the gender ...Post your question